The present application relates generally to systems and methods of inspecting semiconductor wafers, and more specifically to semiconductor wafer inspection systems capable of detecting and characterizing wafer edge defects.
Systems and methods of inspecting semiconductor wafers have traditionally been employed to detect defects occurring on a surface of a semiconductor wafer. For example, conventional laser-based surface scanning inspection systems may operate to detect localized light scatters on a semiconductor wafer surface. Such localized light scatters may be indicative of surface defects that may render one or more integrated circuits fabricated on the wafer surface to be non-functional. Conventional surface scanning inspection systems are typically configured to inspect a wafer surface within a given edge exclusion due to optical artifacts that may result from the edge of the wafer. This limitation of conventional surface scanning inspection systems has generally not impacted the utility of these systems since integrated circuits are normally not fabricated near the wafer edge.
However, even though integrated circuits are not normally fabricated near or on the edge of a semiconductor wafer, it has become increasingly important to detect and to characterize edge defects during semiconductor wafer processing. This is because wafer edge defects often produce flakes of wafer material that may contaminate portions of the wafer on which integrated circuits are subsequently fabricated. Further, mechanical stresses may increase during thermal processing of the wafer, resulting in the formation of cracks in the vicinity of the edge defects. Moreover, an edge defect such as a chip on the wafer edge may compromise the structural integrity of the wafer, allowing cracks to form and subsequently propagate through the bulk wafer material. Such cracks may propagate through one or more integrated circuits fabricated on the wafer, rendering the circuits useless. In addition, because edge defects may compromise the structural integrity of the wafer, the wafer may shatter within a wafer processing chamber, thereby resulting in the loss of the integrated circuits fabricated on the wafer and significant downtime while the processing chamber undergoes re-commissioning.
It would therefore be desirable to have a system and method of inspecting a semiconductor wafer that may be used to detect and to characterize defects occurring on the edge of the wafer. Such a semiconductor wafer inspection system and method would be capable of detecting and characterizing defects in the wafer edge that occur near the wafer surface.